Dysuria can be largely divided into emptying disorder due to inability to urinate with sufficient force at the time of emptying the bladder, and bladder-filling disorder due to inability to retain urine during the filling time. Presently, α1 blocker is frequently used for treating the emptying disorder and anticholine agent, for treating bladder-filling disorder. These drugs, however, have such defects as insufficient long-term therapeutic effect or reduction in quality of life (QOL) induced by side effect, and development of drugs having new activity mechanism different from the conventional approach, for example, drugs utilizing potassium channel opening activity, cyclic guanylate monophosphate (cGMP) decomposition inhibiting activity, are in demand.
cGMP plays an important role in variegated cellular events such as smooth muscle relaxation, memory and learning function control, photoreaction of retina, cell proliferation, immunoreaction and the like, and drop in intracellular cGMP concentration causes disorder in cell functions. Synthesis of cGMP by nitrogen monoxide (NO)-cGMP system and decomposition of cGMP by PDE system are continually progressing in the cells each at a constant rate and good balance of the two are maintained in normal cells. Whereas, within the cells under various states of disorder, function of the NO-cGMP system lowers to render the cGMP synthesis level in the cells low. Because the cGMP decomposition in the cells progresses at a fixed rate in the meantime, cGMP concentration in the affected cells becomes low. It is expected, therefore, prevention of cGMP decomposition in the cells to redress the reduction in intracellular cGMP concentration would be useful for treating or preventing diseases.
While there are many types of PDE, those which specifically decompose cGMP are type 5 (PDE5), type 6 (PDE6) and type 9 (PDE9). Of these, PDE9 shows the least Km value (J. Biol. Chemistry, Vol. 273, No. 25, 15559-15564 (1998), has high affinity to cGMP and is considered to participate in decomposition of cGMP with particular significance.
Heretofore, pyrazolopyrimidine derivatives are known as the compounds exhibiting PDE9-inhibiting activity, and it has been reported as to the derivatives, for example, that they are useful for treating insulin-resistant diseases or the circulatory system disorder, or for improving perception, learning and memory functions (cf. PCT International Publications WO 03/037432 Pamphlet, WO 03/037899 Pamphlet and WO 2004/018474 Pamphlet).
There exists no literature discussing relevancy of PDE9 inhibiting action to therapeutic efficacy of dysuria, however, and not a single quinazoline derivative having PDE9-inhibiting activity is known.
On the other hand, PCT International Publication WO 99/00372 Pamphlet (hereafter referred to as “Literature A”) relates to sulfonamide compounds having PDE5-inhibiting activity, in which 7-carboxy-2-(2,4-dichlorobenzyl)-3-methyl-4(3H)-quinazolinone is specifically disclosed as an intermediate product of their synthesis (cf. Literature A, p. 154, Production Example 43-3). Literature A, however, does not disclose a compound in which the 3-position of quinazoline ring is hydrogen atom and does not contain any description or suggestion on PDE9-inhibiting activity of the compound. We also synthesized 7-carboxy-2-(3-chlorobenzyl)-3-methyl-4(3H)-quinazolinone (hereafter referred to as “Compound A”) and compared PDE9-inhibiting activity of Compound A with that of a compound in which the 3-position of quinazoline ring is hydrogen atom (i.e., the compound of later appearing Example 1) to find the PDE 9-inhibiting activity of Compound A was less than 1/100 that of the compound of the later appearing Example 1, and was extremely low (cf. later appearing Table A showing PDE 9-inhibiting activity of those compounds).